Shortcut Trick
Arrange the given 11 observations in ascending order:
11, 32, 45, 53, 56, 79, 81, 87, 94, 98, 99
Since the number of terms (N = 11) is odd, the median is the exact middle term:
Median = ((11 + 1) ÷ 2)th term = 6th term = 79
∴ The correct answer is 79.
Alternate Method
Given:
Observations: 87, 56, 79, 81, 11, 53, 94, 45, 32, 99, 98
Total number of observations (N) = 11
Formula Used:
When N is odd, Median = ((N + 1) ÷ 2)th term (after arranging in ascending order).
Calculations:
First, arrange the given observations in ascending order:
⇒ 11, 32, 45, 53, 56, 79, 81, 87, 94, 98, 99
Count the total number of observations:
⇒ N = 11
Since N is an odd number, the median is calculated as:
⇒ Median = ((N + 1) ÷ 2)th term
⇒ Median = ((11 + 1) ÷ 2)th term
⇒ Median = (12 ÷ 2)th term
⇒ Median = 6th term
Looking at the ordered list, the 6th term is 79.
⇒ Median = 79
Option Analysis:
⇒ Option (1) 53: This is the 4th term in the sorted list, not the middle term.
⇒ Option (2) 56: This is the 5th term in the sorted list, which is just before the middle term.
⇒ Option (3) 81: This is the 7th term in the sorted list, which is just after the middle term.
⇒ Option (4) 79: This is the exact 6th (middle) term, which is the correct median.
∴ The correct answer is 79.
Additional Information
Median for Even Number of Terms
If the number of observations (N) is even, the median is the average of the (N ÷ 2)th term and the ((N ÷ 2) + 1)th term after arranging them in ascending order.
Relation between Mean, Median, and Mode
For a moderately skewed distribution, the empirical relationship is: Mode = 3 × Median − 2 × Mean.
Effect of Outliers on Median
Unlike the mean, the median is a robust measure of central tendency and is not heavily influenced by extremely large or small values (outliers).